There is this old pc shooting spaceship game....?

where you can shoot things repeatedly with the space bar, I am sure it is not asteroids, it's also where you can enter a pword to a level where most of the time, the background shows a tank with four cannons, 4 cannons on a tank, uhhmm...it's considered to be 2d, along with its terrain to have some shadows on the background, (or land your flying on). And your on a ship...